The ability to synchronize data (voltage, current, time, events, etc.) in a power monitoring system is a valuable tool for end-users. Synchronizing information from power system devices, called intelligent electronic devices (IEDs), is not so much important from a temporal perspective (although it can be used to synchronize clocks) as it is to synchronize data from all IEDs to the same point in time that an event in a power system actually occurred. Although IEDs may record data simultaneously, it is more difficult and expensive to synchronize the IEDs' data together because each IED has its own clock that is used to timestamp when the data was acquired. Because the IEDs' clocks operate independently of each other, the timestamp for an event will be different for each IED. The end-user must synchronize the events manually when analyzing the data, which requires an advanced level of expertise. Global positioning satellite (GPS) time systems can be used, but the end-user has to purchase and install additional hardware and data lines to link the IEDs together and to the satellite system. There are also some limitations for synchronizing data with GPS time systems due to time latencies associated with other hardware in the system, compatibility limitations of hardware, loss of signal from the satellites, and complex configuration of the power system.
Having the IEDs' data synchronized and knowledge of the power system hierarchy provides the basic requirements for many types of sophisticated data analyses, which were previously very expensive and complex. This information can be used to troubleshoot problems, increase equipment and system performance, improve safety, and save money. Automated data synchronization techniques are disclosed in co-pending U.S. patent application Ser. No. 11/174,099, filed Jul. 1, 2005, entitled “Automated Precision Alignment of Data in a Utility Monitoring System”.
All real-world electrical signals in power systems experience subtle changes in their frequency and amplitude over time. The modulation of a power signal's frequency and amplitude are both indeterminate and unique with respect to time. Each IED located on the same electrical grid will experience simultaneously the same frequency fluctuations during steady-state load conditions. IEDs that are directly linked to each other in their respective hierarchy will see a stronger correlation in their amplitude modulation. Frequency and/or amplitude modulation of the signal can be used to precisely synchronize the data of one IED with respect to another IED (or all the IEDs to each other).
The need to synchronize data across multiple power monitoring systems is increasing as the sophistication and sensitiveness of power systems evolve. Synchronizing monitoring system data allows end users to determine how an event propagated through their power system, how it affected their equipment, and potentially how to mitigate reoccurrences.
Systems that use large uninterruptible power supplies (UPSs), such as data centers, server farms, etc., have at least two or more independent grids: the electrical grid from a power utility provider and one or more UPS grids. Because these grids are intentionally isolated from each other and typically operate independently from each other, data synchronization is a challenge. While a solution to align data from the multiple electrical or power grids has been described in co-pending, commonly assigned U.S. patent application Ser. No. 12/262,802, filed Oct. 31, 2008, entitled “Automated Synchronization of Data Between Electrical Grids”, there is presently no solution to automatically identify and place IEDs on their respective grid (heretofore the end-user had to identify which electrical or power grid each discrete IED belonged to). The ability to identify multiple electrical grids and their respective IEDs is an integral part of an automated solution for end-users.
While the data alignment/synchronization algorithms described in U.S. patent application Ser. No. 11/174,099, filed Jul. 1, 2005, entitled “Automated Precision Alignment of Data in a Utility Monitoring System” were originally designed to synchronize data on a uniform electrical grid, methods have been found to ascertain the existence of multiple electrical grids and the placement of discrete IEDs on their respective electrical grid. This disclosure also provides additional error checking capabilities for both the data synchronization results and the spatial alignment results.
What is needed, therefore, is a method for automatically identifying multiple electrical grids in a power monitoring system. The present disclosure is directed to addressing these and other needs.